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If
Ineedn't have got up= Needn't+perfect infinitive or modal verb + have + past participle then what is the answer to;
I've been waiting (for an hour!)
and
(if I) had (a lot of money,) I'd buy (a Ferrari.)
The stuff in brackets doesn't matter! If anyone has an answer I would be soooo, grateful!!!
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Raul, the structure need not + perfect infinitive does exist, and it is not quite the same with the did not have to structure.
Compare:

1. He needn't have woken me up: He did wake me up but that was unnecessary.
2. He didn't have to wake me up: It was not necessary for him to wake me up, but did he? We do not know.

If we say that someone need not have done something, we mean that he or she did it, but it was unnecessary (1). OTOH, if we say that someone did not have to do something, we are simply saying that it was not necessary (whether or not it was done) (2).

As for the question, it is indeed very confusing. Answer to what??!
Comments  
Your question is a bit confusing.

First, the structure is not possible in my opinion. The *** sentence should be:

I didn't have to get up.

"Need" as modal implies necessity, so, if you don't have the necessity of something or doing something, either you "don't need it" or you "don't have to do something".

"I have been waiting..." is correct and it's not a question. What's the problem? Unless it is the answer to a question like:

How long have you been waiting?

"If I had a lot of money I'd buy a Ferrari" is a CONTRARY-TO-FACT conditional sentence. This implies that you actually do not have the money, so you cannot buy you a Ferrri. It's just a supposition. Again, unless it is the answer to a question like:

What would you do if you had a lot of money?

Hope this helps! Emotion: smile
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 Orpheus's reply was promoted to an answer.
Thank you so much for the explanation. I wasn't aware of this difference. Actually, the modal "need" is much more common in BrE and it's been quite a long time since I last heard British English around me. Emotion: smile
No probsEmotion: smile I think you are right about it being another of those UK/US things.
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